Methods and apparatus for wireplasty bone resection

ABSTRACT

A cutting tool to be utilized in the resection or removal of bone tissue from patients includes a handle that tensions a wire or cable-like cutting member with a small diameter between at least two features on the handle to present a thin cutting profile. The design of the cutting tool includes features that protect against soft tissue damage and minimize the incision size necessary to utilize the tool. Some embodiments feature details of the cutting tool that interface with a surgical cutting guide system. Other embodiments describe a cutting tool with a selectively changeable length of the cutting profile of the wire cutting member. In one embodiment, the wire cutting member of the cutting tool is energized by mechanical energy in the form of a unidirectional rotation of the cutting member, a mechanical vibration of the cutting member, or an oscillating movement of the wire cutting member.

CLAIM TO PRIORITY

The present invention claims priority to U.S. Provisional ApplicationNo. 60/540,992, filed Feb. 2, 2004, entitled, “METHODS AND APPARATUS FORWIREPLASTY BONE RESECTION,” and to U.S. patent application Ser. No.11/036,584, filed Jan. 14, 2005, entitled, “METHODS AND APPARATUS FORPINPLASTY BONE RESECTION,” which claims priority to U.S. ProvisionalApplication No. 60/536,320, filed Jan. 14, 2004, entitled, “METHODS ANDAPPARATUS FOR PINPLASTY BONE RESECTION,” the disclosure of each of whichis hereby fully incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to methods and apparatus for boneresection to allow for the interconnection or attachment of variousprosthetic devices with respect to the patient. More particularly, thepresent invention relates to the use of a wireplasty bone resectiontechnique in which wires or cables act as bone cutting tools.

2. Background Art

Different methods and apparatus have been developed in the past toenable a surgeon to remove bony material to create specifically shapedsurfaces in or on a bone for various reasons including to allow forattachment of various devices or objects to the bone. Keeping in mindthat the ultimate goal of any surgical procedure is to restore the bodyto normal function, it is critical that the quality and orientation ofthe cut, as well as the quality of fixation, and the location andorientation of objects or devices attached to the bone, is sufficient toensure proper healing of the body, as well as appropriate mechanicalfunction of the musculoskeletal structure.

In total knee replacements, for example, a series of planar and/orcurvilinear surfaces, or “resections,” are created to allow for theattachment of prosthetic or other devices to the femur, tibia and/orpatella. In the case of the femur, it is common to use the central axisof the femur, the posterior and distal femoral condyles, and/or theanterior distal femoral cortex as guides to determine the location andorientation of distal femoral resections. The location and orientationof these resections are critical in that they dictate the final locationand orientation of the distal femoral implant. It is commonly thoughtthat the location and orientation of the distal femoral implant arecritical factors in the success or failure of the artificial knee joint.Additionally, with any surgical procedure, time is critical, and methodsand apparatus that can save operating room time, are valuable. Pastefforts have not been successful in consistently and/or properlylocating and orienting distal femoral resections in a quick andefficient manner.

The use of oscillating saw blade based resection systems has been thestandard in total knee replacement and other forms of bone resection forover 30 years. Unfortunately, present approaches to using such planarsaw blade instrumentation systems all possess certain limitations andliabilities.

Perhaps the most critical factor in the clinical success of any boneresection for the purpose of creating an implant surface on the bone isthe accuracy of the implant's placement. This can be described by thedegrees of freedom associated with each implant. In the case of a totalknee arthroplasty (TKA), for example, for the femoral component theseinclude location and orientation that may be described as Varus-ValgusAlignment, Rotational Alignment, Flexion-Extension Alignment, A-Plocation, Distal Resection Depth Location, and Mediolateral Location.Conventional instrumentation very often relies on the placement of ⅛ or3/16 inch diameter pin or drill placement in the anterior or distalfaces of the femur for placement of cutting guides. In the case ofposterior referencing systems for TKA, the distal resection cuttingguide is positioned by drilling two long drill bits into the anteriorcortex along the longitudinal axis of the bone. As these long drillscontact the oblique surface of the femur they very often deflect,following the path of least resistance into the bone. As the alignmentguides are disconnected from these cutting guides, the drill pins will“spring” to whatever position was dictated by their deflected coursethus changing their designated, desired alignment to something lesspredictable and/or desirable. This kind of error is further compoundedby the “tolerance stacking,” inherent in the use of multiple alignmentguides and cutting guides.

Another error inherent in these systems further adding to mal-alignmentis deflection of the oscillating saw blade during the cutting process.The use of an oscillating saw blade is very skill intensive as the bladewill also follow the path of least resistance through the bone anddeflect in a manner creating variations in the cut surfaces whichfurther contribute to prosthesis mal-alignment as well as poor fitbetween the prosthesis and the resection surfaces. Despite the fact thatthe oscillating saw has been used in TKA and other bone resectionprocedures for more than 30 years, there are still reports of incidenceswhere poor cuts result in significant gaps in the fit between theimplant and the bone. The safety of these saws is also questionable asminor incidences of misuse can result in serious harm and disability.

While oscillating saws have been the preferred tools for performing boneresections as part of an implantation procedure, other forms of bonesaws and cutting instruments have also been used to cut bones.Generally, the problems of precision, accuracy and safety of these othercutting instruments are even greater than with an oscillating saw. U.S.Pat. No. 5,725,530 describes a planar surgical saw that utilizes a dualchain saw arrangement with guards along the outer sides of the chain sawblades. A surgeon's gigli saw, for example, has a cutting wire with ahandle on each end that is wrapped around a bone to be cut. The surgeonalternates pulling each handle to run the cutting wire back and fortharound the bone to cut the bone. U.S. Pat. No. 4,709,699 describes animproved cutting wire for a surgeon's gigli saw. U.S. Pat. No. 6,368,353describes the use of a gigli saw for resecting the neck of the humerousbone as part of an implant procedure for a shoulder prosthesis. Althoughconventional chain saws and gigli saws can be very efficient generalpurpose cutting tools, these saws have little ability to be guided andaligned so as to make the precise and accurate resection cuts requiredfor effective implants.

Improvements in the precision, accuracy, and safety of tools forresecting bone surfaces are desired in order to increase the efficacy oforthopedic procedures and enable the surgeon to better achieve thebenefits of a standard, less invasive, and more efficacious jointreconstruction.

SUMMARY OF THE INVENTION

The present invention provides for a cutting tool to be utilized in theresection or removal of bone tissue from patients. The cutting toolincludes a handle that tensions a wire or cable-like cutting member witha small diameter between at least two stationary points on the handle topresent a thin cutting profile. The design of the cutting tool includesfeatures that protect against soft tissue damage and minimize theincision size necessary to utilize the tool. Some embodiments featuredetails of the cutting tool that interface with a surgical cutting guidesystem. Other embodiments describe a cutting tool with a selectivelychangeable length of the cutting profile of the wire cutting member. Inone embodiment, the wire cutting member of the cutting tool is energizedby mechanical energy in the form of a unidirectional rotation of thecutting member, a mechanical vibration of the cutting member, or anoscillating movement of the wire cutting member. In another embodiment,a very small diameter wire is used to permit manual manipulation of thecutting tool, but still provide sufficient force to effect cutting ofthe bone.

It is an often repeated rule of thumb for orthopedic surgeons that a“Well placed, but poorly designed implant will perform well clinically,while a poorly placed, well designed implant will perform poorlyclinically.” The present invention provides a method and apparatus forreducing implant placement errors in order to create more reproducible,consistently excellent clinical results in a manner that is lessdependent upon the manual skill of the surgeon creating a resectedsurface. Importantly, some of the embodiments of the present inventiondemonstrate the ability to be inserted into small incisions and yetextend the cutting surfaces of the tool significantly across the bone tobe cut beneath the soft tissues of the joint, thus cutting bone surfacesthat are not readily visible to the surgeon during the procedure.

It should be clear that applications of the present invention is notlimited to Total Knee Arthroplasty, but are rather universallyapplicable to any form of surgical intervention where the resection ofbone is required. These possible applications include, but are notlimited to Unicondylar Knee Replacement, Hip Arthroplasty, AnkleArthroplasty, Spinal Fusion, Osteotomy Procedures (such as High TibialOsteotomy), Bunionectomy, ACL or PCL reconstruction, and many others. Inessence, any application where an inexpensive, accurate, and relativelyprecise system is required or desired for a bone resection is apotential application for this technology. In addition, many of theembodiments shown have unique applicability to minimally invasivesurgical (MIS) procedures and/or for use in conjunction with SurgicalNavigation, Image Guided Surgery, or Computer Aided Surgery systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Other important objects and features of the invention will be apparentfrom the following detailed description of the invention taken inconnection with the accompanying drawings in which:

FIGS. 1 and 2 are pictorial representations of a prior art femoralresection device being used in an open approach TKA and a 19^(th)Century Gigli Saw, respectively, of the prior art.

FIGS. 3-77 show various depictions of the placement and use of wirecutting tools and operation with or without a cutting guide inaccordance with alternate embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 41 shows a Profile Based Resection (PBR) type cutting guidein conjunction with a side cutting drill in action. This will berecognized as an embodiment of the inventions of U.S. Pat. No.5,810,827. The basic components are the side cutting drill, the PBRguide, the guide handle, and fixation features of the cutting guide,which in this case are cannulated screws or drill guides and 0.125 inchdrill pins. The PBR guide possesses at least one plate to which theguide handle is engaged during cutting. A drawback about this particulardesign or embodiment of the PBR technology is that, in the hands of anaverage surgeon, it required an incision length of at least 6 inches inorder to be attached to the femur and utilized to resect or cut bone. Itis an object of some of the embodiments of the present invention toprovide for improvements upon this design enabling it to be used in amanner that is less invasive or minimally invasive while maintaining theoutstanding reproducibility provided by the PBR technology.

FIG. 2 shows an antique gigli saw surgical kit. It is noted that thedate of manufacture of this kit was 1896. The top of the box showncontains the gigli saw, while the bottom of the box shows the handlesused to manipulate the gigli saw in a back-and-forth sawing motion byalternating pulling on each handle.

The present invention provides for a cutting tool to be utilized in theresection or removal of bone tissue from patients. The cutting toolincludes a handle that tensions a wire or cable-like cutting member witha small diameter between at least two stationary points on the handle topresent a thin cutting profile. The design of the cutting tool includesfeatures that protect against soft tissue damage and minimize theincision size necessary to utilize the tool. Some embodiments featuredetails of the cutting tool that interface with a surgical cuttingguide. Other embodiments describe a cutting tool with a selectivelychangeable length of the wire cutting member. In one embodiment, thewire cutting member of the cutting tool is energized by mechanicalenergy in the form of a unidirectional rotation of the cutting member, amechanical vibration of the cutting member, or an oscillating movementof the wire cutting member. In another embodiment, a very small diameterwire is used to permit manual manipulation of the cutting tool, butstill provide sufficient force to effect cutting of the bone.

It should be noted that the manner in which mechanical energy istransmitted to these wire cutting members is shown as being a rotaryinput, or electrical or pneumatic drill. There are many variations whichmay impart improved performance in different ways. For instance, thewire cutting tool shown in FIG. 5 is driven in a fashion reminiscent ofa band saw, but the wire could be a semi-static structure suspendedbetween the two opposing handle arms where ultrasonic energy is impartedto the wire. The advantage to ultrasonic cutting methods is that the‘waveform’ or ‘waveforms’ may be tuned (different frequencies,amplitudes, and waveforms) such that the tool slices through bone like ahot knife through butter, but is incapable or highly resistant toharming soft tissue it contacts. In such an ultrasonic embodiment, thecutting tool preferably has different settings that are selectable bythe surgeon depending on the material he wishes to cut. The mechanicalenergy can also be imparted to the wire cutting elements by commonlyused oscillating saw drivers. FIG. 66 shows a simple embodiment of thepresent invention relying on this form of driver. It is interesting tonote that this embodiment enables the cutting tool, quite uniquely, toeasily create curved surfaces in addition to the continuous, butrectilinear surfaces shown. All that is required is to make the guideslots or surfaces correspondingly curved.

Another embodiment of the present invention does not incorporatemechanical energy applied to the wire cutting member. In thisembodiment, the wire cutting member has an extremely small in diameteror thickness, ideally as small as a single molecule in thickness, andthe wire cutting member is placed under tension. The manual cuttingoperation of this embodiment is similar to that of a cheese slicer. Inessence, the surgeon, by pulling on the handle, imparts sufficient forceto the wire that, given its extremely small thickness, results inexceedingly high contact pressures, thus cutting the bone. Whilemolecular thickness wires are ideal for this embodiment, such as wiresbased on carbon nanotubes, wire thicknesses of 0.005 mm to 0.5 mm aremore practicable.

It will also be recognized that numerous kinds of wires or cables, suchas single stranded or multi-stranded wires, or wires with teeth orprotrusion features or relief features along the wire can be used as thewire cutting member in accordance with the various embodiments of thepresent invention. In the capstan embodiment of the present inventionthat will be described, for example, it is preferred that a wire memberwithout teeth or protrusion members capable of abrading the capstan beused to minimize wear to the capstan drive. Preferably, the effectiveouter diameter of the wire cutting member is no greater than about 4 mmand more preferably less than about 0.5 mm. The wire cutting member maybe formed of metal or a high tensile strength multi or mono-filament,such as Kevlar® fiber. Alternatively, the wire cutting member may beformed of a flexible substrate core adhesively coated with abrasivemedia. Still another embodiment provides for wires spun fromLiquidmetal® alloys. Preferably, the wire cutting member is disposableand is used for a single patient procedure and is then replaced.Alternatively, the wire cutting member can be made sterilizable andreusable.

One important benefit provided by the low thickness wire cutterembodiments of the present invention is the fact that they will cut ormorselize a very small total volume of bone, thus minimizing difficultyin removal of the debris prior to finishing the procedure. In TotalJoint Replacement this is especially important as morselized bone debrisremaining in the joint may lead to premature failure of the bearingcomponents of the implant via the mechanisms of third body wear.

As shown, for example, in FIG. 4, a crank handle can be connected to thecapstan drive input and the cutting wire member manually driven by thesurgeon in a manner similar to that of reeling in a fish with a fishingpole and reel. Although this may sound a bit archaic relative to some ofthe higher technology means disclosed herein, surgeons may prefer thisoption as it provides for outstanding control of the wire, and a directtactile response as the cutting tool is manipulated to cut bone. In thisembodiment of the present invention, to cut a ligament will feeldifferent than cutting bone and in that unlikely event the surgeon willknow immediately that a ligament or other soft tissue is in the way of acut, even though he may not be able to see what is happening. Especiallyin minimally invasive procedures where visibility may be compromised,this additional level of feedback may be very comforting and enablesurgeons to more easily adapt to the demands of less invasive surgery.

Another critical aspect of the present invention is preventing cuttingtools which are capable of cutting soft tissue from coming into contactwith soft tissue, thus damaging the soft tissue. As can be seen in FIGS.23 and 31, the cutting surfaces of the wire extend from a handle surfacein contact with one side of the bone, through the bone, and into anotherhandle surface on the far side of the bone. In this manner, only thehandle surfaces incapable of harming soft tissue are allowed to contactsoft tissue, thus enabling safe use of the wire. If a standardoscillating saw were used to cut, for instance, the neck of the femurthrough a small incision, the saw, having completed the cut, couldaccidentally plunge into the soft tissue on the far side of the bonecausing severe harm to those soft tissues. The ability of the handle toopen and close in response to its engagement to bone, or to a cuttingguide is key in attaining this benefit in many applications.

FIGS. 3-22 show several different embodiments of the present invention.FIGS. 3-11 show a continuous loop embodiment wherein a continuous wireloop is engaged and captured within the guide handle and driven in arotary (like a band saw) or reciprocal motion (like a scroll saw). Oneinteresting feature of this is the capstan drive shown in FIGS. 4, 6 and11, which imparts driving force to the wire and maintains tension in thewire. This mechanism takes advantage of what has been referred to as thecapstan effect, a very effective means of obtaining incrediblemechanical advantage. The mathematic relationships between torque input,capstan or drive input rpm, force input and output, tension, and wirevelocity or surface speed are as follows:

-   -   The relationship between the tensile force exerted on the wire        by the capstan prior to failure of the drive to move the wire        (F_(tmax)), the number of times the wire is wrapped around the        capstan (θ in radians), the dynamic or static coefficient of        friction (μ), and the force resisting movement of the wire at        the moment of failure of the capstan to drive the wire (F_(r))        is—        F _(tmax) =F _(r) e ^((μθ))  (Equation 1)    -   The relationship between torque input to the capstan        (T_(c)—manual or powered), the location of the wire with respect        to the drive axis or centerline of the capstan (R—the effective        radius of contact between the wire and the capstan), and F_(t)        (the tensile force imparted to the wire in operation) is—        F _(t) =T _(c) R  (Equation 2)    -   The relationship between the speed of rotary input (S_(r)), and        the surface or linear speed of the wire (S₁) is—        S ₁ =S _(r) R  (Equation 3)

As shown in FIG. 18, in some applications, it is desirable to enable thearms of the handle to open and close smoothly while cutting bone withoutdemanding the surgeon perform some adjustment of the device that wouldrequire him to delay the cutting process. As the arms open or close, itis desirable to maintain tension on the wire. To enable these desirablegoals, FIG. 6 demonstrates that the capstan can be spring loaded tomaintain firm contact between the wire and the capstan as the arms openand close. Although not shown, it may also be desirable to implement aderailer mechanism similar to that used on 10-speed bicycles to changegears—thus the operator could select a ‘speed setting’ and manipulatethe derailer mechanism to establish the preferred cutting speed.Alternatively, the derailer can be an automatic or semi-automatic devicethat dictates the location of the wire on the capstan as in response towire tension. It is within the scope of the present invention that thecapstan be of any radially concentric geometry, and it is not simplylimited to the conical configuration shown. For instance, the wire cantake the embodiment of a cogged cable or chain wherein the capstan couldtake the form of a gear. Also, the handle can be further biased to forcethe arms of the handle toward open or closed positions during operationto maintain the cutting guide engagement features and/or bone engagementfeatures in contact with cutting guides and/or bone, respectively,without time consuming manipulation of the device by the surgeon (asseen in FIG. 37 where the width of the guide changes along its cuttingpath to enable the guide to conform to the geometry of the boundary ofthe resected surface, and FIG. 24 where no guide is shown but theboundary of the resected surface changes and the engagement features ofthe guide are able to remain in contact with the boundary). It is animportant objective of the present invention to reduce both the amountof time and intellectual effort required to use the invention and thusthe device should be ‘smart,’ automatically doing what the surgeonwishes it to without requiring his attention or conscious interventionregarding the details of the device's operation.

Patient safety is important, but the safety of the surgeon and the ORstaff is also critical. As shown in FIGS. 4, 9 and 10, it may bedesirable to include wire guards that prevent contact between thesurgeon's hands and the wire during handling and use. As gigli saws arecapable of amputating a human femur in a matter of seconds, preventingaccidental contact with the surgeon's fingers or OR staff is key to thesafety design of a wire or cable saw. FIG. 3 shows a differentembodiment of the capstan drive embodiment of the present inventionwhere the capstan is radially expandable to maintain tension and impartdriving force to the wire. This also may be used to keep the wire in asingle plane, as opposed to multiple planes of operation as in FIG. 11,which may help simplify and lessen the cost of the design. Aninteresting safety feature of capstan based embodiments is that if thewire breaks, tension drops to zero instantly and, since the wire hasvery little mass, thus little momentum, the wire will stop movingsimultaneously with breakage. Although not shown in FIG. 6, a mechanismmay be utilized to collapse the capstan spring during assembly tofacilitate ease of assembly.

FIGS. 12-18 show an embodiment of the present invention which mayfurther reduce cost and utilize a wire cutter in a manner similar tothat of the side cutting drill shown in FIG. 1. Once again, a spring isutilized to maintain tension on the wire as the handle arms move towardopened or closed positions (see FIG. 18). In this embodiment of thepresent invention, the wire saw includes a Bushing, a cutting portion,and a drive input (which is square in cross-section in this embodimentfor mating engagement with a square recess in the drive input adapter),as shown in FIGS. 12 and 16. Although this embodiment can bepreassembled for ease of use, economics may make it desirable for thewire saw to be disposable, while the handle is durable, thus requiringpreoperative or intraoperative assembly of the wire saw with the handle.As shown in FIGS. 12-16, assembly of this embodiment could involvethreading the wire through apertures, captured bushings and/or slots inthe handle and engaging the wire drive input feature of this wire cutterembodiment to the drive input adapter. It is of importance to note thatthis embodiment of the present invention provides for complete internalcapture of the wire preventing accidental contact between the wire andeither the patient's soft tissue or the surgeon. Alternatively, ifexposed fixtures are used for threading the wire, a cover member couldbe installed over the wire and exposed fixtures, either prior to use orafter threading the wire through the device, depending upon theparticular embodiment of the cutting tool. Both the Wire Drill Bushingof the wire drill shown in FIG. 6, and the Captured Wire Bushing of theHandle in FIG. 17 act to prevent contact between the features of theHandle and the cutting surfaces of the Wire Drill during use. Inoperation in this embodiment, a powered drill is connected to the wiredrill by way of the Drive Input Adapter, FIG. 16, the wire drill broughtinto contact with bone, and the powered drill actuated to spin thedrill. With a diameter of, for instance, 0.04 inches, it may bedesirable to rotate the wire drill at fairly high rpm to attain thenecessary surface speed to easily resect bone. Balancing out the issueof surface speed is the small contact area between the wire and the bonethus leading to high pressures despite lower force levels. Optimum rpmfor the powered drill in this embodiment will depend upon variousfactors, but drive speeds between 100 rpm and 60,000 rpm will worknicely.

An additional feature that may be desirable to add to differentembodiments of the present invention are the soft tissue protectionsleeves shown in FIGS. 19 and 20. One clinical application calling forthe benefits of this feature would be Transcutaneous Transarticular TKA(“TTTKA” or “Triple TKA” or “T Cubed” or “T³” Procedures) where a PBRcutting guide, as generally shown in FIG. 60 is positioned completelyoutside of the wound with the exception of fixation features whichextend from the externally located guides through skin incisions andinto holes or apertures created in bone. As shown in FIG. 20, thecutting tool, in the case of the present invention a wire, is threadedthrough the handle, the guide, the skin, fat, capsule, etc., (softtissue), across, through, or beneath the articular surfaces of thejoint, and through the soft tissue, guide, and handle on the opposingside of the bone. The soft tissue protection sleeves are then extendedthrough the soft tissue and into contact with the sides of the bone. Theretaining lip can be used to maintain the sleeves in contact with thebone and are held there by the edges of the incision through the capsuleduring cutting. The springs shown in FIGS. 19 and 20 can further biasthe sleeves into contact with bone in a manner that would maintain thatcontact as the width of the bone changed along the cutting path of theresected surface.

One skilled in the art will note that the thicknesses for the softtissue represented in FIG. 20 will change significantly from patient topatient thus requiring the proportions of the sleeve, spring and othercomponents of the present embodiment of the invention to changeaccordingly. For example, in an obese patient, the fat layer throughwhich the cutting tool extends can be 5 inches thick per side or more.The diameter of the soft tissue protection sleeve can be significantlyreduced with respect to what is shown as the wire diameter is so small,thus requiring a smaller capsular incision.

In operation, the handle is manipulated to traverse the cutting path ofthe cutting guide while the tibia is swung through a range of motionabout the femur. This particular principal of operation takes advantageof the fact that the capsule, the patella, and to a lesser or greaterextent the skin, moves with the tibia as it moves through a range ofmotion with respect to the femur. Thus, a small, perhaps 4 mm, stabwound through skin to the medial side of the posterior femoral condyles(roughly in line with the axis of the cutting tool shown in FIG. 60)with the knee bent in flexion, and then looked at the side of the femur(through the portal created by the stab wound) while moving the tibiathrough a range of motion, the side of the femur would be observed to bepassing by/through the portal. In order to complete all of the resectedsurfaces on the femur necessary to fix a standard femoral prosthesis, itmay be necessary in one embodiment to make two passes with the wiresweeping about the femur with the tibia as represented in FIGS. 71 and72.

FIGS. 22-31 show an embodiment of the present invention for use ineither freehand or guided resection of the proximal femur in total hiparthroplasty. Despite fairly large variations in the width of theresected surface along the cutting path of the surface, the contactsurfaces of the handle remain in contact with the bone during freehanduse. As noted herein, this is key in both minimizing the size of theincision necessary to allow passage of the tool into the wound andthroughout boney removal and in preventing the wire from contacting softtissue. In guided use, a pair of guide surfaces could straddle theboundary of the resected surface to be created similar to the guideshown in FIG. 33, but in the hip replacement application it may bedesirable to mount the ‘rails’ on a pivoting mechanism, similar to apair of pliers. Importantly, the cutting path of this kind of cuttingguide preferably needs to geometrically correspond to the cut surface tobe created. This correspondence can be described as having the guidesurfaces being offset from the resected surface by an amount equivalentto the distance between the engagement surfaces of the handle (thatcontact the guide), and the cutting profile of the wire. It should benoted that the guide can be slotted, in which case the retaining clipsshown in FIG. 25 may not be necessary. FIG. 27 shows an alternatecutting path “ending” that allows for complete, or nearly completefemoral preparation without removal of the femoral head from theproximal femur. As limb length discrepancies are a leading cause ofproblems encountered by orthopedic surgeons, determining head and necksizes, lengths, and orientations prior to removing the only directreference to the relationships between final implant location and thepreoperative state would be helpful. In other words, the femoral canalcould be fully or partially prepared to receive the femoral trial stem,the trial stem inserted, fluoroscopic measurements taken of the triallocation and orientation (which is the best predictor of final implantlocation and orientation), the desired neck length and orientationcalculated, and then the femoral neck could be completely resected. Thisshould be extremely useful in avoiding limb length discrepancies, andshould not burden the workflow of the procedure too harshly.

FIGS. 32-41 demonstrate another embodiment of the present invention. Inthis embodiment, an ultralow profile PBR guide is attached to preformedapertures or fixation bases located about the sides of the boundary ofthe resected surfaces to be created. It should be noted that the guidecan be attached to apertures or fixation bases located to the lateralside of the medial condyle and the medial side of the lateral condyle,thus maintaining the stability of this mode of fixation while minimizingdisplacement of soft tissue during the insertion of the guide into thewound and during use. The mediolateral width of the guide surfaces shownin FIG. 37 preferably is no more than 6 mm and can be further reduced toas little as 1 mm, thus minimizing mediolateral soft tissuedisplacement. As seen in FIG. 40, guides of this kind can be utilized inlateral surgical approaches as well as more standard medial or medialparapatellar approaches. Importantly, the guide surfaces for theposterior cut, posterior chamfer cut, and/or distal cut can all bepositioned between the side of the bone and the corresponding collateralligament(s). This is helpful in avoiding contact between the wire andthe soft tissues of the knee joint. While it may be helpful to utilize aretractor to prevent contact between the wire and the posterior cruciateligament (PCL), clinical and cadaveric experience indicates that havingcut the proximal tibia first, placing the knee in deep flexion (greaterthan 100 degrees), and positioning the tibia as far posteriorly withrespect to the femur as possible usually prevents contact between thecutter and the PCL. Of course the guide can also possess a stop featurepreventing movement of the handle and cutter beyond a certain point onthe posterior cut guide surface.

Another point of interest is that, instead of completing all of the cutsin one continuous pass, this guide can be adapted to perform resectionin a more incremental manner that can facilitate even less invasivesurgical techniques. For instance, a single ultralow profile PBR Guidecan be configured to only cut the posterior cut, or alternatively theposterior cut, posterior chamfer cut, and a portion of the distal cut.With the proximal tibia cut and the posterior femoral condylar surfacescut (and the bone chunks removed from the wound), up to a 25 mm gap hasbeen created between the proximal tibial cut and the posterior femoralcut. Thus, if these cut tibial and femoral surfaces are brought intocontact with each other, the soft tissues of the knee joint areamazingly lax allowing for easy insertion of subsequent alignmentguides, cutting guides, handles and cutting tools, including the wirecutting tool of the present invention. Furthermore the remaining cuts(whether that be all cuts except for the already completed posteriorcut, or all cuts except for the already completed posterior cut and/orposterior chamfer cut and/or the distal cut) can be performed with theknee joint in roughly 45 degrees to 15 degrees of flexion to furtherallow for additional laxity of the soft tissues of the knee joint,specifically the extensor mechanism (quadriceps, quadriceps tendon,patella, and patella tendon), thus facilitating ease of implementationof the surgical technique. FIGS. 39 and 40 demonstrate the utility ofthe soft tissue accommodating eccentrically offset contour of the handlewhich facilitates ease of use without requiring dislocation or eversionof the patella. In comparing FIGS. 41 and 40, it is obvious thatultralow profile PBR guides used in conjunction with the handle and wireof the present invention will allow for dramatic reductions in theincision size necessary to accurately, precisely, easily, andinexpensively prepare the bones of a knee joint to receive prostheticimplants.

FIGS. 42-45 demonstrate another embodiment of the present invention foruse in femoral resection and/or tibial resection. FIGS. 42 and 43demonstrate that the natural articular geometry of the femur may beapproximated by two tangent arcs, and that resected surfaces, andthereby the fixation surfaces can be correspondingly curved. FIGS. 44and 45 show another embodiment of the handle of the present inventionthat is attached to apertures drilled in the bone or alternativelyformed in a guide structure located about the sides of the bone, andwhere those apertures are both concentric to and coaxially aligned withthe central axis of the arcs of the resected surface to be created. Thiscan be extremely useful for use in conjunction with a TranscutaneousTransarticular TKA approach (TTTKA), where the aforementioned softtissue protection sleeve embodiment of the present invention is afeature added to the handle shown in FIG. 45 to prevent or mitigatecontact between the wire and soft tissue. Implementing a kinematicresection technique (a term describing cutting one bone of a joint whileswinging the other bone or bones through a range of motion about thefirst) with the TTTKA technique enables absolute minimal soft tissueexposure or intraoperative trauma, as noted previously. As the radius ofthe arcs shown in FIG. 43 may change in size across implant sizes, thehandle or handles preferably possess fixation nubs (perhaps betterreferred to in this embodiment as pivoting nubs) at multiple distancesfrom the cutting profile of the wire. Further, although the arms of thehandle shown in FIGS. 44 and 45 are straight, they may be curved or bentin any configuration to accommodate soft tissues and boney geometry ofthe knee joint whether arms are located partially or completely outsideof the surgical exposure to the joint, or whether they are locatedwithin the exposure entirely. Specifically, the portion of the armsdistally of the pivoting nubs can be configured to reach within theincision of a medial parapatellar exposure, a more medially offsetexposure, or analogous exposures to the lateral side of the joint.

It should be noted that the cuts resulting from the techniques discussedresult in cylindrical cut surface creation, but that the handle can bemodified such that the axis of the pivoting nubs and the axis of thewire suspended between the distal ends of the handle are angled withrespect to each other to enable the creation of cut surfaces that arefrustoconical, resembling a section of a cone, rather than cylindricalsurface. As the lateral condyle, both distally and anteriorly, tends tohave a larger radius or radii than the medial compartment of the kneejoint (somewhat shown in FIG. 42), this enables implant designsminimizing the quantity of viable boney material removal whilefacilitating appropriate implant fixation.

It will be noted that such frustoconical resected surfaces can beresected so as to mate with correspondingly frustoconical fixationsurfaces of an implant, thus creating a progressively greaterinterference fit between the implant and the bone as the implant iscontacted to the cut surfaces and moved laterally across them underforce to achieve press-fit. An exemplary embodiment of an implant thatutilizes such an interference fit with frustoconical resected surfacesis shown in FIG. 77. This embodiment is especially useful in mediallyoriented, less invasive surgical exposures where the ability to insertand impact the implant in a distal to proximal direction is problematicdue to soft tissue interference with implant placement. This sameconcept for implant design is beneficially applied to implants with flatfixation surfaces, or combinations of flat and curved surfaces where themating fit between the implant and the bone is essentially a wedge ofincreasing interference or press-fit as the implant is moved laterally.It should be noted that this same embodiment can be applied to laterallyoriented surgical exposures and adapted accordingly. Frustoconical orwedge like included angles between 1 degrees and 40 degrees will workwell, but in the interests of bone preservation, included angles between1 degrees and 20 degrees are preferred. These embodiments willsignificantly increase the ease of use of attaching femoral implantswherein the arc of the posterior femoral condyles extends beyond 30degrees of arc past the contact point between the femoral and tibialcomponents when the knee is bent to 90 degrees of flexion. It shouldfurther be noted that in one embodiment, the wedge is formed by anincluded angle between the anterior cut(s) and posterior cut(s) onlywhether they are flat or curved. It should be noted that the resectedsurfaces for use with this lateral interference technique may begenerated by any embodiment of the wire cutting tool disclosed herein,or any resection means disclosed in the prior art, or even by simplemodification of standard cutting block designs and alignment techniques.The pinplasty technique described in the provisional patent applicationpreviously incorporated by reference will also work well in creatingsuch surfaces, as would all of the inventions contained in thefollowing: U.S. Pat. Nos. 5,514,139, 5,769,855, 5,643,272, 5,810,827,5,755,803, and U.S. Publ. Application No. U.S. 2002/029038 A1.

Furthermore, as seen in FIGS. 42 and 43, the implementation of curvedposterior cut surfaces enables excellent contact areas between thetibial and femoral implants in deep flexion. The extent of such contactareas between the tibial and femoral implants in deep flexion cancurrently, in terms of commercialized product, only be attained byimplants such as the LPS HiFlex® sold by Zimmer, Inc., of Warsaw, Ind.,which requires a dramatic posterior cut removing bone to a depth ofsomewhere between 12 mm to 19 mm deep because their posterior cut isflat and parallel in at least one plane to the mechanical axis of theleg. Curved resected surfaces enable the same benefits in terms of rangeof motion with excellent contact area (also referred to as conformity)while removing a total volume of living bone from the posterior condylesthat is 50% or less than what is required by the LPS HiFlex®. Thisconservation of living bone not only leaves far more structurally andbiologically viable bone available for any subsequent revision, but alsoconserves structurally viable cortical and dense subcondral bone whichis superior for fixation when compared to the cancellous tissue to whichthe LPS HiFlex® more largely depends on for short and long term fixationduring and after primary procedures.

FIGS. 46-53 show an embodiment of the present invention for use infemoral resection, potentially in a modified form of TTTKA where thesoft tissue portal is only created on one side of the joint. FIG. 46shows a pilot drill that could be guided by manual or computerizedalignment systems to create a hole in bone at or about the joint line.Another embodiment of the wire and handle of the present invention arethen inserted across the joint as shown in FIGS. 47 and 48. A drivemechanism (not shown) is then connected to a manual or powered driver todrive the wire saw to cut bone while moving the tibia through a range ofmotion about the femur, as shown by comparing FIGS. 49 and 50. A simpletwist of the handle, shown in comparing FIGS. 50 and 51 allows forcompletion of the condylar cuts shown in FIG. 53 (note the proximaltibia is represented as having been cut for the sake of clarity). As isevident by examining FIGS. 51 and 52, both the handle and the wire arealmost entirely, and can be easily modified to be entirely, capturedwithin a “tibial bone tunnel,” which prevents any form of contactbetween the wire and soft tissue. Although use in this manner could bedescribed as ‘unguided kinematic resection,’ an alternate embodimentmodifies the embodiment shown to add a single or a plurality ofengagement features to contact a cutting guide located about the sidesof the knee with guide surfaces located outside of the wound, or guidesurface(s) in the wound and outside the wound, or with guide surfaceslocated within the wound. Further, this embodiment or any embodiment ofthe current invention, with no or some modification, can be used inconjunction with the cutting guide inventions shown in the co-pendingprovisional application entitled, “METHOD AND APPARATUS FOR PINPLASTYBONE RESECTION,” U.S. Provisional Application No. 60/536,320, thedisclosure of which is hereby incorporated by reference.

The handle and wire embodiments of the present invention in theembodiment shown in FIG. 47 are modified for use with the Sweeping Guideembodiments of the present invention shown in FIGS. 54-58. In essence,the Sweeping Guides comprise a pivot reference surface and pivotapertures noted in FIGS. 54 and 55 that are positioned and fixed inplace appropriately with respect to the resected surfaces they areintended to create. The Wire Handle Pivot Axis feature represented inFIG. 53 is configured to engage the pivot apertures of the sweepingguide and a contact surface (not shown) on the handle engaged to thepivot reference surface of the sweeping guide. The resulting constructcan then be manipulated by any combination of plunging, sweeping, andchopping movements (not shown) as shown in FIG. 58 to complete thedesired bone cuts. As shown in comparing FIGS. 75 and 76, any of theembodiments of the present invention can be utilized in this manner.Given that the geometric relationships between the anterior cut andanterior chamfer cut with respect to their mutual vertex is consistentfor many implant product lines across multiple or all sizes, a guidelike that shown in FIG. 55 can provide guidance for all implant sizes'anterior and anterior chamfer cuts. Similarly, the guide shown in FIG.56 can be universal to all implant sizes to complete the distal cutand/or distal chamfer cut and/or posterior cut.

FIG. 59 shows apertures created in the bone for fixation of a singlesweeping guide for creating all cut surfaces using a single guideconstruct with 5 pivot apertures and 5 pivot reference surfaces.Although three apertures in bone are shown, two round, or a singlesquare aperture may also be utilized.

FIG. 60 shows an embodiment of the present invention wherein the guideplates and guide surfaces are located entirely outside the wound, butthe wire and handle construct are not passed through mediolateral softtissue portals described hereinabove. The wire controlling portion ofthe handle is essentially ‘snaked’ into the less invasivewound/exposure/approach/incision and the guide engagement features areengaged to the cutting guide at a location entirely outside the wound.As long as the axis of the engagement feature is maintained as coaxialwith the wire, the desired cut geometries will be attained despitemanipulation of the handle with respect to the guide. This method can beutilized to complete some or all of the desired cuts. Also, thisembodiment of the present invention can be used to perform the posteriorcut, posterior chamfer cut, and distal cut optionally using kinematicresection to reduce exposure requirements, and then removed from thewound and guide, flipped over 180 degrees from the orientation shown inFIG. 60, reinserted into the wound and engagement with the guide theanterior chamfer cut and anterior cut completed with or withoutimplementation of a kinematic resection technique and, optionally, withthe knee in 15 degrees to 45 degrees to facilitate the soft tissuelaxity and ease of use hereinbefore described.

FIGS. 61-68 show an embodiment of the present invention for use ineither Unicondylar, Tricompartmental, or Bicompartmental kneearthroplasty. The wire in this embodiment is adapted to be driven by anoscillating saw driver and the wire preferably is formed as a permanentpart of the ‘saw’ as shown in FIG. 65 where the wire is shown in orange,or in an embodiment allowing the wire to be fished through a slot asshown in FIGS. 66-68 and attached to the opposing arm of the saw asshown. The guide of this embodiment of the present invention alsocontains little finger grips enabling a surgeon to attach the cuttingguide to bone about as easily, and in a similar manner to the act ofsecuring separate pieces of paper with a “binder clip” as represented inFIGS. 61, 63 and 64. This allows an oscillating saw driver to be used tocut the continuous and non-colinear cutting path of the cut surfacesshown or continuous and curvilinear cuts while being continuouslymanipulated along the cutting path of the guides without necessarilybeing removed from contact with the guide or bone during the process ofcutting.

FIG. 74 demonstrates an embodiment of the present invention wherein thehandle arm is utilized as an engagement feature for engagement to acutting guide engagement or guide feature and used to guide the wire tocreate the cut surface. Using the handle arm in this manner inconjunction with the medial engagement feature shown in FIG. 74 is alsoan option. In this manner, the wire is manipulated in any manner knownin the art including plunging, chopping, and/or sweeping motions whilethe handle arms open and close to adjust the effective length of thewire available to cut bone thus minimizing the potential for contactbetween the wire and soft tissue and reducing the incision sizenecessary to utilize the embodiments of the present invention.Specifically, the end of the lateral handle arm from which the wireemerges can be used to trace the boundary of the cut surface beingcreated (similar to the method described for the devices in FIGS. 22-31)when the engagement feature is located to the medial side of theboundary. This approach may also be applied to individual condyles ineither TKA, UKA, or bicompartmental procedures. Alternatively, theengagement feature(s) of the cutting guide can be located above thesurface to be created instead of being located completely to the side ofthe boundary. In other words, the cutting guide can include acylindrical aperture whose long axis is roughly normal to a planarsurface to be created and a slit cut along its length to accommodate thewire during insertion and a window roughly normal to the slit throughwhich the wire extends during cutting, where the medial handle arm isalso cylindrical in cross-section to enable smooth articulation with thecylindrical aperture of the cutting guide during cutting. Thecylindrical aperture's long axis can be normal or parallel to the planebeing cut, and it can be located over or alongside the boundary of allthe cuts being made or just an individual resected surface.

It should be noted that, in many of the figures, the cut surface createdby the cutting tool in accordance with the technique of the presentinvention are shown as having already been completed for the sake ofclarity. Similarly, the bones or apparatuses may be shown as beingtransparent or translucent for the sake of clarity. The guides/pins,cutting tool, bones, and other items disclosed are may be similarlyrepresented for the sake of clarity or brevity.

Tibial resection in TKA can be somewhat frustrating to a certainpercentage of orthopedic surgeons. This frustration appears to stem fromthe high demands upon the surgeon's manual skills or craftsmanship. Theforms of the present invention help alleviate this issue by providingpositive guidance of the cutting tool throughout all or most of thecutting process. Also, it should be noted that the various embodimentsof the present invention allow for implementation with very smallincisions.

The complete disclosures of the patents, patent applications andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein.

1. An apparatus for preparing bone to receive an implant fixationsurface comprising; an elongated flexible cutting element adapted to cutbone; a handle having at least a two features defined proximate a distalportion of the handle between which the elongated flexible cuttingelement is tensioned such that the cutting element presents a thincutting profile between the two features that is exposed to and movedacross bone to create the implant fixation surface.
 2. The apparatus ofclaim 1, further comprising means for applying mechanical energy to thecutting element.
 3. The apparatus of claim 2, wherein the means forapplying mechanical energy is selected from the set consisting of: meansfor energizing the cutting element by mechanical energy in the form of aunidirectional rotation of the cutting member, means for providing amechanical vibration of the cutting member, and means for providing anoscillating movement of the wire cutting member.
 4. The apparatus ofclaim 1, wherein the handle is configured to permit at least the distalportion to be inserted into a minimally invasive surgical opening. 5.The apparatus of claim 1, wherein the at least two features areselectively movable relative to one another such that a length of thethin cutting profile dynamically changes in response to a contour of abone as the implant fixation surface is created.
 6. The apparatus ofclaim 1, wherein a volumetric displacement of bone per unit cuttinglength of the thin cutting profile is less than or equal to about 0.2in² per inch cutting length.